This invention relates generally to a method for facilitating Internet Telephony, and more specifically, to the method of connecting Internet Telephony calls.
Internet Telephony makes use of the global connection of the Internet as an alternative voice carrier to enable that voice communications be carried out between different locations around the world. Voice is transmitted as IP packets over the Internet, hence the common term Voice-over-IP (VoIP) used to describe Internet Telephony. One major goal of Internet Telephony is to establish calls in a manner that is as simple as using normal telephone over the Public Switched Telephone Network (PSTN).
One important property of the PSTN network is that all PSTN devices, e.g., telephone sets, connect directly to the PSTN network at all times. When a caller needs to establish a call to another party, the caller needs only dial the telephone number of the party to call. The called party is alerted by the ringing of the telephone upon a successful connection. Both parties start to communicate when the called party picks up the telephone.
In contrast, dial-up Internet Telephony appliances do not attach directly to the Internet and therefore have finite Internet connection time. Internet Telephony requires that the appliances dial-up to the Internet over PSTN before VoIP communication can occur. However, these appliances are normally dormant unless a certain method is devised to generate events that will trigger them to log on to the Internet. These connections normally are only established for as long as they are in use, and are disconnected when they are no longer needed for reason of costs and availability.
Another important aspect of the PSTN infrastructure is the telephone numbering plan. Each PSTN connection has a unique identification or telephone number. A telephone on the PSTN can reach another telephone by simply dialing its unique telephone number.
A dial-up Internet connection in most cases does not have a fixed unique identification. Although each Internet connection does have a unique IP address, dial-up Internet connection is usually assigned with a dynamic IP address that differs each time the dial-up Internet connection is established. For dial-up Internet Telephony to occur, each Internet Telephony user must use a unique identifier and a method that performs translation of this unique identifier to the IP address of its dial-up Internet Telephony appliance.
Various call establishment methods have been adopted for dial-up Internet Telephony based on using existing PSTN and Internet infrastructure. Some of these methods are briefly described below along with their shortcomings.
The xe2x80x9cUser Look-up from Directory Servicesxe2x80x9d method requires the caller to look up the party to call using some form of Directory Services or User Location Services (ULS). All users need to register their user identification and dynamic IP address with the directory server whenever they log on to Internet to use Internet Telephony. A caller will then be able to look up a registered user from a list of users to obtain the user dynamic IP address for establishing a VoIP call. A disadvantage of this method is the fact that a caller can only reach another party that has already logged on to the Internet and has registered with the directory server.
The xe2x80x9cPrearranged Logon Timexe2x80x9d method is an extension of the above method. It basically involves prearranging both users to log on to Internet at a predetermined time to establish a VoIP call. A different method of communication needs to take place for the time to be arranged. Generally, this can be done via an e-mail or a normal telephone call. The caller then obtains the dynamic IP address from a directory server using a known identifier such as an e-mail address. One shortcoming of this method is the inability to establish a VoIP call at anytime.
The xe2x80x9cAuto Logon following Normal Telephone Callxe2x80x9d method removes the need to prearrange time for a VoIP call. A normal telephone call is established when both parties are ready to connect via the Internet and certain buttons or keys are activated. The systems then proceed to identify one another via a communication method while still connected as a normal telephone call. When this is done, the normal telephone call disconnects and the systems automatically log on to Internet. The dynamic IP address is then obtained from a directory server to establish a VoIP call. A disadvantage of this method is the cost of the required normal telephone call prior to establishing a VoIP call.
The xe2x80x9cAuto Logon Dedicated Linexe2x80x9d method is normally used to bypass the need to incur the cost of a normal telephone call prior to establishing a VoIP call. The system is configured to log on to Internet automatically every time a call is detected on the line and then proceeds to register itself with a directory server. The caller system needs to know the number of the called party and uses this to look up the dynamic IP address from the directory server. A VoIP call is then established. A shortcoming of this method is the fact that a dedicated line needs to be used for VoIP call since all incoming call will be treated as a VoIP call.
Hence, there is a need for a method of establishing a VoIP call for dial-up Internet Telephony appliances that notifies the called party to log on to the Internet with minimal interference to the normal usage of the telephone, transparently acquires the address of the called party using a mechanism to translate a unique identifier to IP address so as to not require prior arrangement to log on to Internet at a prearranged time, does not incur PSTN call charges for establishing PSTN-to-PSTN voice call prior to VoIP call, receives normal PSTN telephone calls as well as VoIP calls, and requires minimum technical and new usage knowledge required for a user to make a VoIP call.
This new call establishment method for Internet Telephony appliances includes two phases. The first phase is a method of notifying the Internet Telephony appliance of the called party that a VoIP call is being attempted. The second phase is for both systems to automatically log on to the Internet and to proceed through the procedure to establish the VoIP call. The nature of directory server and VoIP protocol is the choice of a particular implementation as this method is independent of any specific directory services or VoIP protocols. The following pseudo-codes and illustrations indicate the steps involved at both the caller""s system (local device) and the called party""s system (remote device) when making a VoIP call.